The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventor(s), to the extent the work is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art, are neither expressly nor impliedly admitted as prior art against the present disclosure.
High speed limiting amplifiers used in optical communication and high speed analog front-ends used in electrical signaling require the use of high bandwidth amplifiers that can amplify small input signals and/or equalize channel loss, preferably with as little signal degradation as possible and with a minimum of additionally required components. While improvements to semiconductor processing technologies have led to circuits with somewhat greater reliability, linearity, and noise characteristics, comparable advances in circuit abstraction and layout continue to play a role in the sustained improvement of amplifier performance, and in some instances, are the only means to overcoming emerging technological obstacles.
One parameter affecting the performance of amplifiers is low frequency (e.g., DC) offset, which may take the form of difference voltages or currents between the differential output terminals. In general, differential signals transmitted through a high-speed amplifier may suffer distortions or imperfections due to a semiconductor device mismatch, interconnect mismatch, and/or trace defects along the amplifier chain. These imperfections, often caused by random mismatches in the signal path resulting from the semiconductor etching process, may disadvantageously cause variations in the common-mode of the differential signal, lead to lower sensitivity, and can also impact chip yield. Frequently, these random variations may present themselves as a DC offset on the differential signal. Thus, offset in amplifier circuits tends to degrade circuit performance.